1. Field of the Invention
The present invention relates to an auto document feeder that supplies each of a plurality of documents to a predetermined read position, the document feeder being used in a digital copier or the like which copies an image from a document or the like to a sheet.
2. Description of the Related Art
Image forming apparatuses such as digital copiers are provided with an auto document feeder (ADF) based on what is called a sheet through scheme; the auto document feeder loads and conveys each document to a read position in a document reader.
In an image forming apparatus provided with the auto document feeder based on the sheet-through scheme, a glass plate (read surface) is provided at a read position in the document reader. An image is read from a document being conveyed, through the glass plate.
The auto document feeder based on the sheet-through scheme comprises a plurality of conveying rollers that convey a loaded document, stabilizing roller located at the read position of the glass plate to stabilize the behavior of the document, and guide member placed upstream of the read position of the glass plate to guide the document along a glass surface.
As a technique relating to the sheet-through scheme, an image reader has been disclosed which has a specified spacing between a backup roller and contact glass (see, for example, Jpn. Pat. Appln. KOKAI Publication No. 9-27889).
It is known that, with the auto document feeder based on the sheet-through scheme, the quality of a read image is affected by the spacings between the glass plate and the stabilizing roller and between the glass plate and the guide member. It is also known that, particularly with a color copier, these spacings significantly affect the quality of the read image. However, in conventional auto document feeders, these spacings are not optimized, thus disadvantageously preventing sufficient image quality from being achieved.